Swami Prabhavana says that try to focus on one thing. The mind flickers continuously, so in a purified mind that focus will happen easily. In Dharna it will settle down for at least some continuous time - Krishna and the mantra of Krishna or whatever form of Shiva and Om Namashivai. Not interrupted by anything else.
Swami Sarvapriyananda teaches Chapter 6 (Verses 20-21) of the Bhagavad Gita. In this series of talks, Swami Sarvapriyananda unfolds the highest truths of Vedanta through the study of the Bhagavad Gita (The Song of God).